<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>debug</title>
    <script>
        /* debug */
        console.log(d);
        var a = 10;
        var b = "hello";
        c = true;

        function fun() {
            console.log("hello");
        }
        var d = 23;
    </script>
</head>

<body>

</body>

</html>